Re: Not sure why.
Athens also had a strong tradition of public service, about as strong as our obsession with commercial success. If you could afford armour, you became a hoplite. If you could afford a horse, you rode in the cavalry. Any fool could teach himself to be a peltast (a sling man, firing missiles over the heads of the phalanx at the enemy. Those who could do nothing else could man an oar in a trireme.
Athens' major line of defense, the fleet, was manned by privately sponsored ships crewed by poor, but free citizens). Can you imagine Bank of America or Exxon offering to subsidize an aircraft carrier or nuke submarine today? Only if they could sell it to the highest bidder, even if it was the other side.